[Beagle8U]

"Just to let you know, Republicans have an open primary in Michigan, the Rats have a caucus. So they can/do vote in both."

Its not quite an open primary. You must declare a party before either primary, and once you do, you can't vote in the other primary.

[Springman]

In Warren, I never had to, just select which party to vote. Couldn't cross over vote.

Guess that was a nice thing about the old style voting machines.